Jack a good boy today.（杰克今天很乖）
A: is
B: is being
C: was
D: am
A: is
B: is being
C: was
D: am
举一反三
- The boy ____ ill today. A: are B: is C: be D: am
- 今天我值日。 A: I am on duty today. B: I am in duty today. C: I am with duty today. D: I am at duty today.
- Either Jack or I ______ to blame. A: to be B: being C: am D: are
- Jack is very good at __________ excuses for being late.
- Mary ______ a good girl today. A: is to be B: is C: has been D: is being